Abbott, Joyce, Morrison and the other MPs who abstained

Vote on the Marriage Amendment Bill at Parliament House in Canberra on Thursday 7 December 2017. fedpol Photo: Alex Ellinghausen

Former Australian Prime Minister Tony Abbott leaves after speaking during debate of the Marriage Amendment Bill in the House of Representatives at Parliament House in Canberra, Thursday, December 7, 2017. (AAP Image/Lukas Coch) NO ARCHIVING

When it came to the final vote on same-sex marriage, it was standing room only on the "yes" side of the House of Representatives, while a lonely group of just four "no" voters perched on the other side.

But some MPs were missing from the historic event.

The House of Representatives does not officially record MPs who abstain, but is estimated about 14 MPs did not vote on the same-sex marriage bill.

This included some of Parliament's most high profile "no" advocates, including Treasurer Scott Morrison, former prime minister Tony Abbott and former defence minister Kevin Andrews. Deputy Prime Minister Barnaby Joyce was also among the group, along with renegade Liberal Nationals MP George Christensen, conservative West Australian Liberal Andrew Hastie and Assistant Health Minister David Gillespie.

Government frontbenchers Michael Sukkar??? and Alex Hawke are also understood to have abstained from the vote on Thursday evening.

Former Labor treasurer Wayne Swan - a supporter of same-sex marriage - was also missing from the final vote. He was not in Parliament on Thursday, but was given a "pair", meaning another MP on the government side also sat the vote out.

While abstaining could be interpreted as fence-sitting on a controversial issue, many MPs have explained they chose to forgo their votes to try and accommodate both their personal views on same-sex marriage and the clear majority "yes" vote in the postal survey. Others have added that had the bill been amended to include more protections for freedom of speech and religion, they may have voted differently.

Mr Abbott had previously said the postal survey result "should be respected - respected by the community, respected by the Parliament". In Mr Abbott's Sydney electorate of Warringah, 75 per cent of eligible residents voted "yes".

Mr Joyce, who believes in the "traditional form" of marriage told Parliament on Thursday he had separated from his wife, adding he did not pretend to be "any sort of saint". In an interview with 2GB on Friday, Mr Joyce explained he had made the revelation because he didn't want to look like a hypocrite.

Mr Andrews has written an entire book on the importance of marriage between a man and a woman. He said he did not want to "stand in the way" of the survey result but "could not positively vote for a bill which failed to protect freedom of conscience and belief".

Earlier on Thursday, Prime Minister Malcolm Turnbull and Foreign Minister Julie Bishop abstained from some of the votes on amendments to the bill.

These included the failed proposal from Mr Sukkar to include two definitions of marriage (one for straight couples, one for gay couples) and amendments from Mr Hastie, which included the right of parents to take their children out of classes that talk about same-sex marriage (which was also unsuccessful). When asked, their offices did not give explanations for their absence.

In the upper house last week, 12 senators voted "no", and eight more abstained on the final same-sex marriage vote. These included Employment Minister Michaelia Cash, Labor's Deb O'Neil and One Nation's Pauline Hanson.

South Australian Liberal David Fawcett also abstained from the final Senate vote, despite leading the charge to amend the bill in the upper house.

Senator Fawcett explained he needed to abstain because he could not in "good conscience" support a bill for same-sex marriage, but at the same time wanted to respect the majority "yes" outcome of the postal survey.

"Not every issue is black and white," he said. "Sometimes [abstaining] is the only way if you want to be true to your conscience."